Cogito Ergo Sum - Predecessors

Predecessors

Although the idea expressed in Cogito ergo sum is widely attributed to Descartes, he was not the first to mention it. Plato spoke about the "knowledge of knowledge" (Greek νόησις νοήσεως - nóesis noéseos) and Aristotle explains the idea in full length:

But if life itself is good and pleasant (...) and if one who sees is conscious that he sees, one who hears that he hears, one who walks that he walks and similarly for all the other human activities there is a faculty that is conscious of their exercise, so that whenever we perceive, we are conscious that we perceive, and whenever we think, we are conscious that we think, and to be conscious that we are perceiving or thinking is to be conscious that we exist... (Nicomachean Ethics, 1170a25 ff.)

Augustine of Hippo in De Civitate Dei writes Si fallor, sum ("If I am mistaken, I am") (book XI, 26), and also anticipates modern refutations of the concept. Furthermore, in the Enchiridion Augustine attempts to refute skepticism by stating, "y not positively affirming that they are alive, the skeptics ward off the appearance of error in themselves, yet they do make errors simply by showing themselves alive; one cannot err who is not alive. That we live is therefore not only true, but it is altogether certain as well" (Chapter 7 section 20). Another predecessor was Avicenna's "Floating Man" thought experiment on human self-awareness and self-consciousness.

The 9th Century Hindu philosopher, Shankaracharya, wrote in a similar fashion, No one thinks, 'I am not', arguing that one's existence cannot be doubted, as there must be someone there to doubt.